Pipelines transporting liquid or gaseous materials often extend through areas where the pipeline needs to be weighted to avoid having the pipeline being lifted or heaved by buoyant forces or frost. Such areas include, for example, underwater, marsh, muskeg, and other unconsolidated environments. A trench is typically formed, the pipeline is installed in the trench, and sections of the pipeline are anchored, coated, or weighted with concrete, clamp on weights, or bag weights filled with weighting fill material. The weighted or anchored pipeline must thereafter resist hydrostatic forces of flooding, or freeze-thaw cycles.
Early pipeline weights included simple or complex concrete or concrete-containing devices which could be placed on or strapped around the pipeline. Exemplary patents include U.S. Pat. No. 2,662,552, issued Dec. 15, 1953 to Rowe et al.; Canadian Patent 1,021,952 issued Dec. 6, 1977 to Bunn; U.S. Pat. No. 4,166,710, issued Sep. 4, 1979 to Spiridonov; Canadian Patent 1,021,952 issued Dec. 6, 1977 to Bunn; Canadian Patent 2,158,801 issued Jul. 14, 1998 to Key-May Industries Ltd.; French Patent Application No. 2,716,251 A1 of Bouygues Offshore Société, published Aug. 18, 1995; and U.S. Pat. No. 5,443,329 issued Aug. 22, 1995 to Spuncon Pty. Ltd. and Marecon Pty.
Bag weights for pipeline weighting have been more recently used. They are advantageous in that they can be filled with inexpensive weighting fill materials such as sand and gravel at remote locations during pipeline installation. The bag weights limit damage to a pipeline protective coating. Exemplary patents include U.S. Pat. No. 3,793,845 issued Feb. 26, 1974 to Keith; Canadian Patent 2,075,006, issued Jul. 16, 2002, to Connors; Canadian Patent 2,277,523 issued Feb. 17, 2004, to Jewell; and Canadian Patent Application 2,527,790 published May 22, 2006 to Tiger Ridge Resources Ltd.
Several of the bag weights of the above patents present problems in the filling and installation operations. The bag weights, once filled, may be very large and heavy, for example in excess of 10,000 pounds. The Connors' device has side saddle bags that are open along its upper longitudinal edges, making spillage of the fill material problematic. As well, these open bags allow water to enter the bag, causing the bag contents to freeze in cold climates where these bags are often used. Installation of frozen bags is problematic, both in terms of awkward handling, and pipe damage. The Connors' device has been altered from that shown in the patent to include drawstrings, partial stitching or flaps to close or partially close these upper edges. These efforts have complicated both the manufacturing of the bags, and the filling and installation process, without fully addressing the problems of spillage and freezing. The Jewell device requires a difficult under the pipeline strapping and cinching operation to fix the bag weights onto the pipeline. Since the bag weights are placed over the pipeline in the close confines of a trench, the strapping operation can be difficult and dangerous for workers, particularly for very large bags which hang well below the pipe. Both the Connors' and Jewell devices cause difficulties with the large bag sizes, since the bag, to provide the needed weight, enlarge both the depth and width dimensions of the weighted pipeline. This in turn increases the depth and size of the trench that is needed to accommodate the weighted pipeline.
The Tiger Ridge device uses a circumferential cinch that requires workers to wrap a strap more than one circumferential distance around the bag and pipeline, which can be a difficult operation in the confines of the pipeline trench. As noted above, large bag weights that extend either too far above, or too far below the pipeline require the trench to be excavated to depths that may be uneconomical. The Tiger Ridge device attempts to address this problem by filling with heavy barite material, however, barite material is not always readily available or available at low cost.
As well, the heavy bag weights are typically end filled by suspending the bag weight above ground from the open bag ends, and filling each bag from an overhead hopper (see for example Canadian Patent 2,431,281, issued Jun. 13, 2006 to Jewell). The bag ends must then be individually rolled over and tied to close the ends, a labor intensive process. As well, the ends can open after tying, spilling fill material.
A simple, inexpensive pipeline weighting device is still needed to address one or more of the above-noted problems.